The present invention relates to a centrifugal separator, more specifically a centrifugal separator of cake bottom discharge type comprising a rotatable basket and a drive unit thereof on a top lid, wherein a cake is discharged from the bottom of an outer case.
In the production of medicines, chemicals, foods, etc., measures for preventing introduction of foreign substances into the products must be strictly carried out. Particularly, medicines and their raw materials, which need to be produced according to GNP (Good Manufacturing Practice), should be treated even more strictly to prevent introduction of foreign substances.
When producing medicines and the like, centrifugal separators are often used for separating a material slurry into solid and liquid components. When a material slurry is changed to another kind of material slurry, the centrifugal separator has to be thoroughly cleaned so that the residual raw materials are removed therefrom.
Thus, the centrifugal separators for such applications require consideration for its inner surface to be cleaned. In particular, it is desired for the centrifugal separators that cleaning operation is easy (operability); cleaning can be conducted entirely and thoroughly (cleanability); cleaned parts can be visually observed without difficulty after cleaning (visual observability); and the surroundings of the separator are prevented from contamination with a spent cleaning water (antipollution property), etc.
Heretofore, in the production of medicines and the like, the separation of slurries into solid and liquid components is often conducted using centrifugal separators which have a rotatable basket and a drive unit therefor attached to a top lid and discharge cakes from the bottom of an outer case, i.e., so-called bottom discharge type centrifugal separators. The following are typical examples of this type of centrifugal separators: (a) a centrifugal separator comprising an outer case fixedly mounted on a stand via supporting legs; a top lid equipped with a rotatable basket and a drive unit therefor and mounted on said outer case in a upwardly movable manner; a top lid lifting device which lifts said top lid together with said rotatable basket, when cleaning is operated, to bring said rotatable basket outside said outer case, thereby allowing cleaning the inside of said outer case and said rotatable basket separately (b) a centrifugal separator with the similar structure as that of the above (a) further comprising a cleaning hole in the side wall of the outer case, and a lid of the cleaning hole which is removed when cleaning is carried out so that the inside of the outer case and the rotatable basket can be cleaned through the cleaning hole with the top lid kept on the outer case.
The former centrifugal separator (a) has good cleanability and visual observability because the rotatable basket can be cleaned outside the outer case. However, when cleaning the rotatable basket, a cleaning liquid spreads outside the outer case, resulting in contamination of the surroundings of the apparatus. Thus, the former centrifugal separator has a poor antipollution property. In addition, the top lid, which is equipped with the rotatable basket, the drive unit therefor and many other auxiliary devices, is considerably heavy and troublesome to be lifted up. Moreover, a part of auxiliary devices such as a slurry feeding port, electric wires provided on the top lid have to be temporarily removed therefrom. The removing and resetting of the auxiliary devices are troublesome and pose a problem in operability of the centrifugal separator.
The latter centrifugal separator (b) is free from the problems of the former typo centrifugal separator since the latter does not require lifting the top lid or does not cause spread-out of the cleaning liquid. However, it is impossible to see the inside of the entire outer case and the rotatable basket through the cleaning hole, and therefore insufficiently cleaned parts may remain. Besides, it is difficult to visually check the result of cleaning, offering problems in cleanability and visual observability.
Thus, the conventional centrifugal separators (a) and (b) have both advantages and disadvantages and improvement thereon is being required.
It is a principal object of the present invention to provide a centrifugal separator of cake bottom discharge type and has excellent operability, cleanability, visual observability and antipollution property.
It is another object of the present invention to provide a centrifugal separator of the above type, wherein a rotatable basket is detachably attached to a drive shaft, and therefore can be cleaned separately from the drive shafts, and the rotatable basket is easily attachable onto the drive shaft after cleaning.
It is another object of the present invention to provide a centrifugal separator of the above type, wherein screws of the drive shaft are replaceable when damaged, so that the drive shaft need not be wholly replaced.
Other features of the present invention will be apparent from the following description.
The present Invention provides a centrifugal separator, wherein a rotatable basket and a drive unit therefor are mounted on a top lid; a cake outlet is provided at the bottom of the rotatable basket and an outer case; the top lid is fixedly mounted on a stand via supporting legs; the outer case is supported by and mounted on the top lid; when cleaning is carried out the outer case can be detached from the top lid; the outer case is downwardly movable when detached form the top lid; the rotatable basket can be exposed to the outside by this downward movement.
In the present invention, the rotational basket is removably attached to its drive shaft. A fastening device is provided at the lower end of the drive shaft in order to fasten the rotatable basket on the drive shaft. The fastening device comprises a bolt member which is connectable coaxially in the axial direction to the lower end of the drive shaft by the operation from the radial direction and a nut member screwed onto the bolt member. The nut member may be selectively screwed at either a first position, a lower part of the bolt member, or a second position, an upper part of the bolt member. When the nut member is at the first position, the bolt member can be coaxially connected to the drive shaft; when the nut member is at the second position, the rotatable basket can be fastened to the drive shaft and the bolt member can be held in a coaxially connected state.
In a preferable fastening device, the drive shaft has a cutout extending upward in an axial direction thereof to occupy a part of the periphery of its lower end portion, and a cavity for engagement which extends radially inward from the surface of the cutout. The bolt member comprises an upright portion projecting upright in the radial direction from part of the periphery of its upper end, and an engaging projection projecting radially from the upright portion. The upright portion and the projection of the bolt member are engaged with the cutout and the cavity of the drive shaft toward the radial direction, whereby the bolt member can be connected to the lower end portion of the drive shaft in axial alignment and the nut member can be screwed on the bolt member. The nut member, when screwed in this manner, can be selectively positioned either at the first position In which the upright portion and the projection are exposed to the outside, or at the second position in which the upright portion and the projection are housed inside of the nut member so as to fasten the rotatable basket.